CVE-2020-17496
CVE-2020-17496 is a security flaw in vBulletin. Attackers can run their own code on vBulletin. The US Cybersecurity and Infrastructure Security Agency (CISA) added it to its catalog of flaws known to be used in attacks on 3 Nov 2021.[1]
vBulletin is business software or equipment. Most families won’t have it, but attackers break into it to get inside companies, and from there to what those companies hold about their customers, patients and staff. vBulletin has published a fix or advice.
Description
CISA calls it a PHP module remote code execution in vBulletin vBulletin. In its words: “The PHP module within vBulletin contains an unspecified vulnerability that allows for remote code execution via crafted subWidgets data in an ajax/render/widget_tabbedcontainer_tab_panel request. This CVE ID resolves an incomplete patch for CVE-2019-16759.”[1]
The underlying weakness is CWE-74, in MITRE’s list of common software weaknesses.[2]
It scores 9.8 out of 10 on the Common Vulnerability Scoring System, which rates it critical, scored by NVD using CVSS 3.1.[2]
Affected versions
NVD’s record doesn’t list version ranges for it; vBulletin’s advisory has them[3]. CISA names the product as vBulletin vBulletin.
Most families won’t have vBulletin; it’s for whoever looks after IT at work.
Exploitation
CISA added it to its catalog of known exploited vulnerabilities on 3 Nov 2021, 448 days after it was made public. CISA lists a flaw only when it has reliable evidence of it being exploited, and gave US federal agencies until 3 May 2022 to fix it.[1]
FIRST’s Exploit Prediction Scoring System, which estimates how likely a flaw is to be used in attacks in the next 30 days from what it sees across the internet, puts it at 87%. That’s in the top 1% of the flaws it scores.[4]
CISA assesses it as automatable: attackers can run it against many targets at once.
CISA doesn’t say who was attacked, or how.
Fix
vBulletin has published a fix or advice.[3] CISA’s required action: “Apply updates per vendor instructions.”[1]
- Check whether you use it.vBulletin is business software or equipment, so most families won’t have it. If you run a business, or work from home on company equipment, ask whoever looks after your IT.
- Send this page to your IT person.Ask them to confirm it’s fixed, or not in use. CISA gave US government agencies until 3 May 2022 to fix it.
- If it can’t be fixed, take it offline.CISA’s advice when there’s no fix is to stop using the product, or take it off the internet, until there is one.
You can’t fix someone else’s server, but you can watch for what follows a break-in like this: a breach notice, a password reset you didn’t ask for, or a scam message that knows things it shouldn’t. HARD watches for those for you and your family.
Timeline
| Date | Event |
|---|---|
| The flaw is made public in the National Vulnerability Database, with a severity score of 9.8.[2] | |
| CISA adds it to its catalog of flaws known to be used in attacks.[1] | |
| CISA’s deadline for US government agencies to fix it.[1] | |
| FIRST puts the odds of it being used in attacks in the next 30 days at 87%.[4] |
See also
Other vBulletin flaws
- CVE-2019-16759: PHP module remote code execution ·
Similar flaws
- CVE-2025-20337, Cisco Identity Services Engine: injection ·
- CVE-2025-20281, Cisco Identity Services Engine: injection ·
- CVE-2022-43769, Hitachi Vantara Pentaho Business Analytics (BA) Server: pentaho BA server special element injection ·
- CVE-2023-22527, Atlassian Confluence Data Center and Server: template injection ·
- CVE-2022-35914, Teclib GLPI: remote code execution ·
Added the same day
- CVE-2021-42258, BQE BillQuick Web Suite: SQL injection ·
- CVE-2021-42013, Apache HTTP Server: path traversal ·
- CVE-2021-41773, Apache HTTP Server: path traversal ·
- CVE-2021-40539, Zoho ManageEngine: aDSelfService plus authentication bypass ·
- CVE-2021-40444, Microsoft MSHTML: remote code execution ·
References
- ^ Cybersecurity and Infrastructure Security Agency. “vBulletin PHP Module Remote Code Execution Vulnerability”. Known Exploited Vulnerabilities Catalog, added 3 Nov 2021.
- ^ National Institute of Standards and Technology. “CVE-2020-17496 Detail”. National Vulnerability Database, published 12 Aug 2020.
- ^ vBulletin. Advisories and fixes: forum.vbulletin.com.
- ^ FIRST. “Exploit Prediction Scoring System”. EPSS 0.875, percentile 99.8, 31 Oct 2026.
- CVE Program. “CVE-2020-17496”. The official CVE record.
This article is built from CISA’s catalog (version 2026.10.30), NVD’s record and FIRST’s scores, kept in HARD’s database and checked every morning. The plain English is HARD’s.